adam_mac84

Can anyone who has one of these bikes grab these measurements for me? Bigger frame the better, but i should be able to extrapolate the geometry to a larger frame if need be (brush off that old trigonometry). I will be looking specifically toward the Le Champion (deciding between sram and ultegra).

Thanks.

(fwiw, if anyone doesn't know, this is stack and reach)
I recently learned of it from slowtwitch, that is where pic is taken from

(stack can be measured ground to BB, subtracted from ground to top of head tube)

DaveSSS 

Just because a person owns on of these bikes doesn't make this easy to measure with sufficient accuracy to be of value. For a reach measurement to be of any value, it has to be taken at the exact stack height that you need.

There are better ways to compare frames, when the stack and reach are not listed.

Why not explain what you are trying to do? It's usually more efficient to just compare the head tube length, then compare the TT length, with corrections for any difference in the seat tube angle.

Reach is just the TT length minus the frame setback. Frame setback is the c-c frame size times the cosine of the STA.

https://www.motobecane.com/rdcarbon/cfltd.html#geo

adam_mac84

I want to compare it to a few bikes i have also been considering and riding... specifically my motobecane fantom, fuji SST, Raleigh comp, and spec allez/secteur.

Being tall, it is pretty easy to get low enough on any bike (frame size will be in the 61cm range).

Sorry if i asked for the wrong measurements to approximate fit. Thanks for the feedback!!! I am very comfortable with setup of a bike after i have it, i was just looking to see if there were a bike that i could approximate these figures, as i also was under the impression that most steerers were cut to a 'standard' stack height that could then be adjusted from there (as suggested by my LBS).

Supposedly the LE Champion is moto's between bike between their 'comfort' (century) and 'race' geometry (immortal). Based on my test rides, i am leaning toward a race geometry set up on the upright side because i do still like some drop and the more responsive steering of these type of bikes.

I thought HT/TT length combined with seat angle could be misleading with the different 'angles' or slopes of top tubes. In my mind if 2 bikes had similar HT/ST ANGLES, but one had horizontal TT, and one had upsloping TT that would change the stack because while angles were similar, the one with an upsloping TT would have a higher stack and slightly shorter reach. (does that make sense?) I suppose that is where HT LENGTH comes into play.

DaveSSS 

All geometry charts will list a TT length that is measured horizontally, even if the TT slopes. Sometimes it's referred to as "virtual" or "effective", but all it means is horizontal.

You can compare the head tube lengths, if the frames use the same type of headset (integrated or conventional). If not, then you need to compensate for the difference in stack height. The integrated types vary from 8-20mm and conventionals are in the 25-35mm range. Both can have up 4cm of spacer used under the stem. That amount of spacer used under the stem can be changed and so can the stem angle, to alter the handlebar height.

The problem with trying to compare the Le Champion to the Immortal is that the geometry charts fail to list the critical head tube length. The Immortal actually has a shorter TT length and the same STA, so it has a shorter reach. The odd thing about it is the head tube angle of only 72.5 degrees, which would be more relaxed than the Le Champion, unless the listing is a mistake and it's really 73.5.

The head tube on the immortal might be shorter, but you would need to contact Motobcane to find out. It's sad when a manufacturer isn't smart enough to list all of the critical dimensions.

adam_mac84

Thanks again Dave. I contacted BD to find out lengths on HT. I have been test riding more bikes, and paying close attention to how the spacers/stem are set up, as well as finding the geometry specs online to compare all things. Realistically, how much of a difference will 0.5* make on a seat/head tube angle?

I also understand that ride comfort can be greatly affected by tire/rim combo, so i try to remain more neutral on that aspect. (i usually ride 25c tires)

DaveSSS 

A steeper STA will increase the reach by about 8-10mm per degree, depending on the frame size, so it can be significant. The HTA makes very little difference in the fit, but it changes the steering trail. A bike with a .5 degree steeper HTA will have less steering trail and steer more quickly, IF it has the same amount of fork offset. For offset also changes the trail, but not in the direction that some people think. More offset reduces the trail and also quickens the steering.

To figure the trail, you can go to an online calculator, or use the formula R/tanH - (offset/sinH) where R is the tire radius and H is the head tube angle.

adam_mac84

Oh boy, now im really deep into all of this stuff!!! I have found the head tube heights on many of the bikes that i rode from the Specialized Allez (230mm), to the raleigh competition (200) to the SST (180), and on some of the endurance bikes like Cannondale Synapse (220) to specialized secteur (245)

Interesting that the allez which is a 'race' geometry is longer head tube than the endurance synapse (allez has 1* steeper steerer)

DaveSSS 

Also remember that bikes that are new will most often have the maximum amount of spacer under the stem - not really what you want to use, if the bike fits properly. Stem angles can also vary greatly. If a bike has a +6 degree stem and 4cm of spacer, the bars will be about 6cm higher than the lowest possible position (no spacer and a -17 degree stem.